1. Field of the Invention
This invention relates to furniture of the type having at least first and second movable drawers and, more particularly, to a locking mechanism that prevents simultaneous movement of the first and second drawers from a closed state into an open state.
2. Background Art
Many furniture systems, such as filing cabinets, have drawers stacked in a vertical column. Depending upon the distribution of the contents of the drawers, simultaneous opening of the drawers could cause the entire cabinet to tip. This condition may occur not only when a user intentionally withdraws multiple drawers, but may occur during an earthquake or when a cabinet is inadvertently tipped, as during transportation or relocation thereof.
To alleviate this problem, a number of locking mechanisms have been devised which are activated upon the opening of one drawer and prevent the withdrawal/opening of one or more additional drawers simultaneously with the one drawer.
One such system uses a slide bar that is guided in vertical movement relative to a frame within which the drawers are mounted. The slide bar has cantilevered pins which project into the path of an actuator on each drawer. The drawers will open only with the slide bar in a first vertical position. By opening one of the drawers, the slide bar is shifted by the actuator on the opening drawer vertically from the first vertical position into a second vertical position to block the remaining drawers from opening. Two examples of this type of system are disclosed in U.S. Pat. No. 4,609,233 (Walla) and U.S. Pat. No. 4,925,257 (Frederiksen et al.).
While the above type of system operates effectively, it has a number of drawbacks. First of all, the actuators on the drawers and the slide bars may need to be manufactured and assembled to within relatively close tolerances. Otherwise, the parts could jam, which could result in the locking system malfunctioning and/or the drawers being obstructed from moving smoothly, or prevented from moving at all.
Another problem with the above type of systems is that the lock bar is commonly mounted in a recessed guide track in the furniture frame. As a result, formation of the track introduces another step in the manufacture of the frame, which potentially adds significantly to manufacturing cost. Precise formation and location of the guide track may be required.
The following patents show different types of locking mechanisms: Mitchell, U.S. Pat. No. 3,199,937; Friend, U.S. Pat. No. 3,259,444; Olree, U.S. Pat. No. 3,454,320; Anderson, U.S. Pat. No. 3,881,792; Blouin, U.S. Pat. No. 4,429,930; Craig, U.S. Pat. No. 4,705,326; Lakso, U.S. Pat. No. 4,711,505; Pham, U.S. Pat. No. 4,955,672; Scheerhorn, U.S. Pat. No. 5,056,876; Mitchell, U.S. Pat. No. 5,176,436; McGregor, U.S. Pat. No. 5,333,949; Hartrum et al., U.S. Pat. No. 5,335,986; and Hubbard et al., U.S. Pat. No. 5,586,817. Certain of these systems use a relatively large number of parts. Others require relatively precise alignment of parts, absent which proper function may be impaired or prevented. As noted above, generally, the more complicated is the assembly of such systems, the more expensive becomes manufacturing, ultimately adding to the cost of the product to the end user.